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Knox R, Brennan-Minnella AM, Lu F, Yang D, Nakazawa T, Yamamoto T, Swanson RA, Ferriero DM, Jiang X. NR2B phosphorylation at tyrosine 1472 contributes to brain injury in a rodent model of neonatal hypoxia-ischemia. Stroke 2014; 45:3040-7. [PMID: 25158771 DOI: 10.1161/strokeaha.114.006170] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND AND PURPOSE The NR2B subunit of the N-methyl-d-aspartate (NMDA) receptor is phosphorylated by the Src family kinase Fyn in brain, with tyrosine (Y) 1472 as the major phosphorylation site. Although Y1472 phosphorylation is important for synaptic plasticity, it is unknown whether it is involved in NMDA receptor-mediated excitotoxicity in neonatal brain hypoxia-ischemia (HI). This study was designed to elucidate the specific role of Y1472 phosphorylation of NR2B in neonatal HI in vivo and in NMDA-mediated neuronal death in vitro. METHODS Neonatal mice with a knockin mutation of Y1472 to phenylalanine (YF-KI) and their wild-type littermates were subjected to HI using the Vannucci model. Brains were scored 5 days later for damage using cresyl violet and iron staining. Western blotting and immunoprecipitation were performed to determine NR2B tyrosine phosphorylation. Expression of NADPH oxidase subunits and superoxide production were measured in vivo. NMDA-induced calcium response, superoxide formation, and cell death were evaluated in primary cortical neurons. RESULTS After neonatal HI, YF-KI mice have reduced expression of NADPH oxidase subunit gp91phox and p47phox and superoxide production, lower activity of proteases implicated in necrotic and apoptotic cell death, and less brain damage when compared with the wild-type mice. In vitro, YF-KI mutation diminishes superoxide generation in response to NMDA without effect on calcium accumulation and inhibits NMDA and glutamate-induced cell death. CONCLUSIONS Upregulation of NR2B phosphorylation at Y1472 after neonatal HI is involved in superoxide-mediated oxidative stress and contributes to brain injury.
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Affiliation(s)
- Renatta Knox
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Angela M Brennan-Minnella
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Fuxin Lu
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Diana Yang
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Takanobu Nakazawa
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Tadashi Yamamoto
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Raymond A Swanson
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Donna M Ferriero
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.)
| | - Xiangning Jiang
- From the Department of Pediatrics (R.K., F.L., D.Y., D.M.F., X.J.), Biomedical Sciences Graduate Program (R.K., D.M.F.), Medical Scientist Training Program (R.K.), Department of Neurology (A.M.B.-M., R.A.S., D.M.F.), and San Francisco Veterans Affairs Medical Center (A.M.B.-M., R.A.S.), University of California, San Francisco; and Division of Oncology, Institute of Medical Science, The University of Tokyo, Tokyo, Japan (T.N., T.Y.).
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Gross C, Bassell GJ. Neuron-specific regulation of class I PI3K catalytic subunits and their dysfunction in brain disorders. Front Mol Neurosci 2014; 7:12. [PMID: 24592210 PMCID: PMC3923137 DOI: 10.3389/fnmol.2014.00012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 01/28/2014] [Indexed: 11/13/2022] Open
Abstract
The phosphoinositide 3-kinase (PI3K) complex plays important roles in virtually all cells of the body. The enzymatic activity of PI3K to phosphorylate phosphoinositides in the membrane is mediated by a group of catalytic and regulatory subunits. Among those, the class I catalytic subunits, p110α, p110β, p110γ, and p110δ, have recently drawn attention in the neuroscience field due to their specific dysregulation in diverse brain disorders. While in non-neuronal cells these catalytic subunits may have partially redundant functions, there is increasing evidence that in neurons their roles are more specialized, and confined to distinct receptor-dependent pathways. This review will summarize the emerging role of class I PI3K catalytic subunits in neurotransmitter-regulated neuronal signaling, and their dysfunction in a variety of neurological diseases, including fragile X syndrome, schizophrenia, and epilepsy. We will discuss recent literature describing the use of PI3K subunit-selective inhibitors to rescue brain disease-associated phenotypes in in vitro and animal models. These studies give rise to the exciting prospect that these drugs, originally designed for cancer treatment, may be repurposed as therapeutic drugs for brain disorders in the future.
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Affiliation(s)
- Christina Gross
- Department of Cell Biology, Emory University School of Medicine Atlanta, GA, USA ; Center for Translational Social Neuroscience, Emory University School of Medicine Atlanta, GA, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine Atlanta, GA, USA ; Center for Translational Social Neuroscience, Emory University School of Medicine Atlanta, GA, USA ; Department of Neurology, Emory University School of Medicine Atlanta, GA, USA
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Lai TW, Zhang S, Wang YT. Excitotoxicity and stroke: identifying novel targets for neuroprotection. Prog Neurobiol 2013; 115:157-88. [PMID: 24361499 DOI: 10.1016/j.pneurobio.2013.11.006] [Citation(s) in RCA: 775] [Impact Index Per Article: 70.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/28/2013] [Accepted: 11/29/2013] [Indexed: 01/22/2023]
Abstract
Excitotoxicity, the specific type of neurotoxicity mediated by glutamate, may be the missing link between ischemia and neuronal death, and intervening the mechanistic steps that lead to excitotoxicity can prevent stroke damage. Interest in excitotoxicity began fifty years ago when monosodium glutamate was found to be neurotoxic. Evidence soon demonstrated that glutamate is not only the primary excitatory neurotransmitter in the adult brain, but also a critical transmitter for signaling neurons to degenerate following stroke. The finding led to a number of clinical trials that tested inhibitors of excitotoxicity in stroke patients. Glutamate exerts its function in large by activating the calcium-permeable ionotropic NMDA receptor (NMDAR), and different subpopulations of the NMDAR may generate different functional outputs, depending on the signaling proteins directly bound or indirectly coupled to its large cytoplasmic tail. Synaptic activity activates the GluN2A subunit-containing NMDAR, leading to activation of the pro-survival signaling proteins Akt, ERK, and CREB. During a brief episode of ischemia, the extracellular glutamate concentration rises abruptly, and stimulation of the GluN2B-containing NMDAR in the extrasynaptic sites triggers excitotoxic neuronal death via PTEN, cdk5, and DAPK1, which are directly bound to the NMDAR, nNOS, which is indirectly coupled to the NMDAR via PSD95, and calpain, p25, STEP, p38, JNK, and SREBP1, which are further downstream. This review aims to provide a comprehensive summary of the literature on excitotoxicity and our perspectives on how the new generation of excitotoxicity inhibitors may succeed despite the failure of the previous generation of drugs.
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Affiliation(s)
- Ted Weita Lai
- Graduate Institute of Clinical Medical Science, China Medical University, 91 Hsueh-Shih Road, 40402 Taichung, Taiwan; Translational Medicine Research Center, China Medical University Hospital, 2 Yu-De Road, 40447 Taichung, Taiwan.
| | - Shu Zhang
- Translational Medicine Research Center, China Medical University Hospital, 2 Yu-De Road, 40447 Taichung, Taiwan; Brain Research Center, University of British Columbia, 2211 Wesbrook Mall, V6T 2B5 Vancouver, Canada
| | - Yu Tian Wang
- Brain Research Center, University of British Columbia, 2211 Wesbrook Mall, V6T 2B5 Vancouver, Canada.
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Mechanisms of rapid reactive oxygen species generation in response to cytosolic Ca2+ or Zn2+ loads in cortical neurons. PLoS One 2013; 8:e83347. [PMID: 24340096 PMCID: PMC3858366 DOI: 10.1371/journal.pone.0083347] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Accepted: 11/01/2013] [Indexed: 12/16/2022] Open
Abstract
Excessive “excitotoxic” accumulation of Ca2+ and Zn2+ within neurons contributes to neurodegeneration in pathological conditions including ischemia. Putative early targets of these ions, both of which are linked to increased reactive oxygen species (ROS) generation, are mitochondria and the cytosolic enzyme, NADPH oxidase (NOX). The present study uses primary cortical neuronal cultures to examine respective contributions of mitochondria and NOX to ROS generation in response to Ca2+ or Zn2+ loading. Induction of rapid cytosolic accumulation of either Ca2+ (via NMDA exposure) or Zn2+ (via Zn2+/Pyrithione exposure in 0 Ca2+) caused sharp cytosolic rises in these ions, as well as a strong and rapid increase in ROS generation. Inhibition of NOX activation significantly reduced the Ca2+-induced ROS production with little effect on the Zn2+- triggered ROS generation. Conversely, dissipation of the mitochondrial electrochemical gradient increased the cytosolic Ca2+ or Zn2+ rises caused by these exposures, consistent with inhibition of mitochondrial uptake of these ions. However, such disruption of mitochondrial function markedly suppressed the Zn2+-triggered ROS, while partially attenuating the Ca2+-triggered ROS. Furthermore, block of the mitochondrial Ca2+ uniporter (MCU), through which Zn2+ as well as Ca2+ can enter the mitochondrial matrix, substantially diminished Zn2+ triggered ROS production, suggesting that the ROS generation occurs specifically in response to Zn2+ entry into mitochondria. Finally, in the presence of the sulfhydryl-oxidizing agent 2,2'-dithiodipyridine, which impairs Zn2+ binding to cytosolic metalloproteins, far lower Zn2+ exposures were able to induce mitochondrial Zn2+ uptake and consequent ROS generation. Thus, whereas rapid acute accumulation of Zn2+ and Ca2+ each can trigger injurious ROS generation, Zn2+ entry into mitochondria via the MCU may do so with particular potency. This may be of particular relevance to conditions like ischemia in which cytosolic Zn2+ buffering is impaired due to acidosis and oxidative stress.
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Luo P, Yang Y, Liu W, Rao W, Bian H, Li X, Chen T, Liu M, Zhao Y, Dai S, Yan X, Fei Z. Downregulation of postsynaptic density-95-interacting regulator of spine morphogenesis reduces glutamate-induced excitotoxicity by differentially regulating glutamate receptors in rat cortical neurons. FEBS J 2013; 280:6114-27. [PMID: 24103031 DOI: 10.1111/febs.12531] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 09/08/2013] [Accepted: 09/12/2013] [Indexed: 01/03/2023]
Abstract
Glutamate-induced excitotoxicity is involved in many neurological diseases. Preso, a novel postsynaptic scaffold protein, mediates excitatory synaptic transmission and various synaptic functions. In this study, we investigated the role of Preso in the regulation of glutamate-induced excitotoxicity in rat cortical neurons. Knockdown of Preso with small interfering RNA improved neuronal viability and attenuated the elevation of lactate dehydrogenase (LDH) release after glutamate treatment. Downregulation of Preso also inhibited an increase in the BAX/Bcl-2 ratio and cleavage of caspase-9 and caspase-3. Although the expression and distribution of metabotropic glutamate receptor (mGluR) 1/5, NR1, NR2A and NR2B were not changed by knockdown of Preso, downregulation of Preso protected neurons from glutamate-induced excitotoxicity by inhibiting mGluR and N-methyl-D-aspartate receptor function. However, downregulation of Preso neither affected the expression of GluR1 and GluR2 nor influenced the function of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor after glutamate treatment. Furthermore, intracellular Ca(2+) was an important downstream effector of Preso in the regulation of excitotoxicity. These results suggest that expression of Preso promotes the induction of excitotoxicity by facilitating different glutamate receptor signaling pathways. Therefore, Preso might be a potential pharmacological target for preventing and treating neurological diseases.
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Affiliation(s)
- Peng Luo
- Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi'an, China
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Eckert A, Nisbet R, Grimm A, Götz J. March separate, strike together--role of phosphorylated TAU in mitochondrial dysfunction in Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2013; 1842:1258-66. [PMID: 24051203 DOI: 10.1016/j.bbadis.2013.08.013] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 08/08/2013] [Accepted: 08/12/2013] [Indexed: 12/17/2022]
Abstract
The energy demand and calcium buffering requirements of the brain are met by the high number of mitochondria in neurons and in these, especially at the synapses. Mitochondria are the major producer of reactive oxygen species (ROS); at the same time, they are damaged by ROS that are induced by abnormal protein aggregates that characterize human neurodegenerative diseases such as Alzheimer's disease (AD). Because synaptic mitochondria are long-lived, any damage exerted by these aggregates impacts severely on neuronal function. Here we review how increased TAU, a defining feature of AD and related tauopathies, impairs mitochondrial function by following the principle: 'March separate, strike together!' In the presence of amyloid-β, TAU's toxicity is augmented suggesting synergistic pathomechanisms. In order to restore mitochondrial functions in neurodegeneration as a means of therapeutic intervention it will be important to integrate the various aspects of dysfunction and get a handle on targeting distinct cell types and subcellular compartments.
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Affiliation(s)
- Anne Eckert
- Neurobiology Laboratory, Psychiatric University Clinics Basel, University of Basel, Switzerland
| | - Rebecca Nisbet
- Centre for Ageing Dementia Research (CADR), Queensland Brain Institute (QBI), The University of Queensland, Australia
| | - Amandine Grimm
- Neurobiology Laboratory, Psychiatric University Clinics Basel, University of Basel, Switzerland
| | - Jürgen Götz
- Centre for Ageing Dementia Research (CADR), Queensland Brain Institute (QBI), The University of Queensland, Australia.
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